Research Project: Reducing the Environmental Footprint from Agricultural Systems through Managing Resources and Nutrient Inputs

Location: Soil, Water & Air Resources Research

2020 Annual Report

Objectives
Objective 1: Characterize and improve accounting of N emissions as N2O and NH3 losses from cropping systems. Subobjective 1.1: Quantify the soil and environmental factors contributing to N2O production by nitrifying and denitrifying bacteria. Subobjective 1.2: Assess the effect of cover crops on N2O production in the field. Subobjective 1.3: Assess manure injection/incorporation methods for impact on residue/surface cover, soil disturbance, and N emissions. Objective 2: Enhance process-level characterization of agrochemical emissions, fate and transport across spatial scales from micro-environments to regions. Subobjective 2.1: Determine the effect tillage practices have on agrochemical volatilization losses from agricultural fields. Subobjective 2.2: Improve measurement and modeling approaches to describe agrochemical emissions and transport from agricultural operations. Subobjective 2.3: Determine the emission flux of NH3 and other gases from cattle feedlot surfaces using flux-gradient technique. Subobjective 2.4: Compare particulate plume data measured with LiDaR to conventional model (ex. AERMOD) predictions to assess model accuracy for both near facility and downwind transport. Subobjective 2.5: Develop an improved physics-based model on the dispersion of herbicide droplets from mechanical sprayers by incorporating ambient turbulence conditions, the turbulent kinetic energy generated by the motion of the sprayer, and atmospheric stability. Objective 3: Develop strategies to manage the effects of manure properties and air flow on NH3 emissions. Subobjective 3.1: Manipulate swine diet formulations to improve N utilization, and reduce N excretion and NH3 emission along with other gaseous emission into the environment. Subobjective 3.2: Evaluate and develop ventilation practices for reducing NH3 and other air quality emissions.

Approach
This project will focus on knowledge gaps that exist in the loss of N and agrochemicals from cropping and animal systems. Three approaches will be pursued for addressing knowledge gaps: 1) quantify soil and environmental factors contributing to N2O and NH3 emissions in animal production and field cropping systems; 2) determine soil properties that drive volatile loss and transport of agrochemicals and N compounds, and 3) determine effectiveness of N control strategies for reducing NH3 emissions. In cropping systems, there are large gaps in our understanding of the N budget in soil including both mechanisms and magnitude of losses through emissions. Laboratory studies on N2O emissions will use stable isotopes to quantify both the effect of temperature and kinetics of denitrification under varying NH3 concentrations. Field studies using chambers will be used to quantify N2O emission for a range of soil and nitrogen management strategies. Assessing the effect residue/surface cover and soil disturbance have on N loss from manure application in cropping systems will be conducted during late fall and early spring. Whole field emissions loss of N will be quantified using both an open path laser system coupled with inverse dispersion modeling for NH3 and eddy covariance with a quantum cascade laser system for N2O emissions. Quantifying the transport parameters controlling volatile losses of pesticides from cropping systems based on tillage practices will use eddy covariance micrometeorology techniques to determine turbulent flux from whole fields. The relaxed eddy accumulation technique will be used to provide more accurate eddy diffusivities for pesticide vapor transport to improve agrochemical volatilization flux estimates. In addition, LiDaR will be used to develop dispersion models for droplets from mechanical sprayers for physics-based models on the loss of agrochemicals from fields due to spray drift. Quantifying the transport parameters controlling volatile losses of N compounds and particulates from animal production systems will involve LiDaR- to measure plume dynamics and produce a remote-sensing approach to quantify emissions and compare these results to conventional modeling approaches. In animal production systems, NH3 is the dominant form of N emissions, but gaps exist in effective N control/mitigation strategies that reduce N emissions. Reducing NH3 emissions from animal production will focus on improving N utilization in animal diets by use of feed additives and improving grind size of feed particles. Ventilation practices will be evaluating and optimized for reducing NH3 emissions. Knowledge gained through this research will provide producers and regulatory agencies scientific data to improve sustainability of agricultural production facilities in U.S. farming systems.

Progress Report
Objective 1: Field monitoring study was conducted to quantify nitrous oxide (N2O) emission under various tillage and cover crop production practices. For corn, no-till and no-till with rye cover-crop management systems reduced N2O emissions by 40% and 50%, respectively, and for soybeans, tillage and cover crops had no effect on N2O emissions. Shifts in the management system to accommodate a winter camelina cash crop erased the N2O gains associated with the no-till and cover crop treatments for corn production. Future analysis will focus on the timing of N2O emissions to inform management practices to balance N2O loss with system productivity. Monitored spring field application of manure from a swine finishing operation using a dragline manure transport. Loss of ammonia (NH3) occurred primarily over the first three days after manure application and continued for more than seven days. Loss of NH3 was higher for manure applied using truck transport compared to manure pumped to field using a dragline, but the loss was not significant. More work needs to be done to confirm this observation. Future work is expanding the number of fields monitored and using an unmanned aerial vehicle for assessing field conditions. Objective 2: A relaxed eddy accumulation pesticide flux system was beta tested. The system was run for five days in a field that was treated with metolachlor and atrazine. Vertical wind away from the soil surface was correlated with metolachlor concentrations indicating volatilized herbicide was transported away from the soil surface to the atmosphere. However, additional vertical winds in the downward direction toward the soil surface were also correlated with metolachlor but at lower concentrations. The dual nature of pesticide transport is consistent with turbulence transport theory. Future work will be focused on determining the net (upward -downward) flux of field applied metolachlor and atrazine from bare soil. A spray drift experiment to measure the impact of a large moving tractor with spray implements on turbulence during a spray event used four eddy covariance (EC) systems at different heights. The EC design allowed for measuring disturbances in turbulence momentum and vertical velocity during a spray event. As the spray rig moved through the field past the EC systems, the EC systems measured distinct episodic vertical wind velocities at the leading edge of the tractor. This observation confirmed the hypothesis that a large bluff body such as a tractor spray rig produces enough momentum to transfer winds in the upward direction away from the soil surface. This upward movement results in spray droplets being ejected upwards more than 10 m above the ground surface and increasing the potential loss of herbicides through spray drift. However, due to the loss of the LiDAR instrumentation and retirement of a key collaborator, this project has been terminated. Ammonia emission flux from cattle feedlot surfaces was modeled using Windtrax software based on recommendations from the EPA-USDA ammonia working group. Screening parameters were set-up on turbulence data. Preliminary data runs showed that the area associated with high animal activity (loading areas) had increased NH3 emissions compared to holding pens and that extreme weather events with high winds lead to emissions fluxes almost an order of magnitude higher than under typical conditions. In future analysis, pen moisture, animal density, and weather conditions will be correlated with NH3 emission fluxes. Objective 3: A monitoring study was started to compare indoor air quality in tunnel ventilated buildings without pit-fans. In general, barn concentrations of NH3, CH4, and H2S were highest near the fan, while particulate matter (PM) and CO2 were lowest near fans. These results suggest that the source of PM and CO2 originated mainly from animals and feed and NH3, CH4, and H2S originated from manure. As the animals matured, PM and CH4 and H2S concentrations all increased, whereas, NH3 concentration tracked more with the outdoor temperature and ventilation than animal maturity. In future research, the tracking of C, N and S in the animal diet with animal growth, gas emission, and manure is being considered. Agitation of swine manure in pits beneath the confinement buildings and pumping for manure application to fields are the most odor intensive events associated with swine finishing operations. Manure samples from a swine feeding trial were agitated to simulate a pumping event and gas emissions was monitored. Agitation increased CH4 and H2S emissions by two orders of magnitude and doubled carbon dioxide emissions, while ammonia remained largely the same. Odor from volatile sulfur compounds rose rapidly with agitation and accounted for over 98% of the total odor. In general, volatile organic compound emissions remained largely unchanged with agitation except for ketone and alcohol compounds that increased by an order of magnitude but were minor odorants overall. This work informs researchers which compounds are the most problematic in terms of odor during agitation and gives scientist and engineers targets for controlling odor during agitation and pumping of manure for field application.

Accomplishments
1. Dietary particle size formulation effect on manure and odor emissions. Nutrients excreted from livestock affect manure and gas composition emitted from manure storage facilities. ARS researchers in Ames, Iowa, in collaboration with an Iowa State University researcher conducted a swine feeding trial to evaluate potential interactive effects between feed particle size and diet composition on manure and gas emissions. In general, diets higher in fiber increased manure nitrogen (N), carbon (C), and total volatile fatty acid (VFA) concentrations, and increased manure VFA emissions, but decreased manure ammonia emissions. Decreasing the particle size of the diet lowered manure N, C, VFA, phenolics, and indole concentrations, and decreased manure emissions of total VFA. Neither diet composition nor particle size had an impact on manure greenhouse gas emissions. Information from this research will be useful for growers and engineers as they consider formulations technologies to reduce manure output and gas emissions.

2. Swine manure management odor control. Manure management systems have a major impact on odor from swine finishing operations. ARS researchers in Ames, Iowa, and Florence, South Carolina in collaboration with scientists from South Korea and Iowa State University compared deep-pit manure management systems to flushing barn manure management systems for odor reduction and organic matter digestion. Total solids (TS) in the manure were positively correlated to total nitrogen, total carbon, volatile fatty acids (VFA), phenol compounds, indole compounds, and volatilized odorants including VFAs, ammonia, phenol compounds, and indole compounds. Carbon dioxide was the main C source evolved averaging over 90% of the carbon evolved. Methane production increased significantly with dilution. Diluting manure by four-fold reduced TS and headspace odorants by equal amounts and doubled the rate of organic matter consumption, but high levels of dilution increased overall manure volume. Information from this research will be useful for growers and engineers as they consider manure management flushing systems impact on odor control and manure treatment.

Review Publications
Trabue, S.L., Kerr, B.J., Scoggin, K.D. 2019. Swine diets impact manure characteristics and gas emissions: Part I sulfur level. Science of the Total Environment. 687:800-807. https://doi.org/10.1016/j.scitotenv.2019.06.130.
Logsdon, S.D., Cambardella, C.A., Prueger, J.H. 2019. Technique to determine water uptake in organic plots. Agronomy Journal. 111(4):1940-1945. https://doi.org/10.2134/agronj2018.10.0641.
Dold, C., Hatfield, J.L., Prueger, J.H., Moorman, T.B., Sauer, T.J., Cosh, M.H., Drewry, D.T., Wacha, K.M. 2019. Upscaling Gross Primary Production in corn-soybean rotation systems in the Midwest. Remote Sensing. 11(14):1688. https://doi.org/10.3390/rs11141688.
Reichle, R., Liu, Q., Koster, R., Crow, W.T., Delannoy, G., Kimball, J., Ardizzone, J., Bosch, D.D., Colliander, A., Cosh, M.H., Kolassa, Mahanama, S., McNairn, H., Prueger, J.H., Starks, P.J., Walker, J. 2020. Version 4 of the SMAP level-4 soil moisture algorithm and data product. Journal of Advances in Modeling Earth Systems. 11:3106-3130. https://doi.org/10.1029/2019MS001729.
Knipper, K.R., Kustas, W.P., Anderson, M.C., Alsina, M., Hain, C., Alfieri, J.G., Prueger, J.H., Gao, F.N., McKee, L.G., Sanchez, L. 2019. Using high-spatiotemporal thermal satellite ET retrievals for near-real time water use and stress monitoring in a California vineyard. Remote Sensing. 11(18):2124. https://doi.org/10.3390/rs11182124.
Kraatz, S., Jacobs, J., Schroeder, R., Cho, E., Cosh, M.H., Seyfried, M.S., Prueger, J.H., Livingston, S.J. 2019. Evaluation of SMAP freeze/thaw retrieval accuracy at core validation sites in the contiguous United States. Remote Sensing. 10(9):1483. https://doi.org/10.3390/rs10091483.
Walker, V., Hornbuckle, B., Cosh, M.H., Prueger, J.H. 2019. Seasonal evaluation of SMAP soil moisture in the U.S. corn belt. Remote Sensing. 11(21):248. https://doi.org/10.3390/rs11212488.
Hatfield, J.L., Prueger, J.H., Sauer, T.J., Dold, C., O'Brien, P.L., Wacha, K.M. 2019. Applications of vegetative indices from remote sensing to agriculture: past and future. Inventions. 4(4):71. https://doi.org/10.3390/inventions4040071.
Aboutalebi, M., Torres, A., McKee, M., Kustas, W.P., Nieto, H., Alsana, M., White, W.A., Prueger, J.H., McKee, L.G., Alfieri, J.G., Hipps, L., Coopmans, C., Dokoozlian, N. 2019. Incorporation of unmanned aerial vehicle (UAV) point cloud product into remote sensing evapotranspiration models. Remote Sensing. 12(1):50. https://doi.org/10.3390/rs12010050.
Wilson, T.G., Kustas, W.P., Alfieri, J.G., Anderson, M.C., Prueger, J.H., McKee, L.G., Alsina, M., Sanchez, L., Alsted, K. 2020. Relationships between soil water content, evapotranspiration, and irrigation measurements in a California drip-irrigated Pinot noir vineyard. Agricultural Water Management. https://doi.org/10.1016/j.agwat.2020.106186.
Trabue, S.L., Kerr, B.J., Scoggin, K.D. 2019. Swine diets impact manure characteristics and gas emissions: Part II Sulfur source. Science of the Total Environment. 698:1115-1124. https://doi.org/10.1016/j.scitotenv.2019.06.272.